Electrochemical nanoneedle biosensor based on multiwall carbon nanotube

We report the fabrication and analytical functions of a biosensor based on a nanoneedle consisting of a multiwall carbon nanotube attached to the end of an etched tungsten tip. The devised electrode is the smallest needle-type biosensor reported to date. The nanoneedles prepared in this work are 30 nm in diameter and 2-3 mu m in length. Dopamine and glutamate, which are physiologically important neurotransmitters, were successfully detected using these nanoneedles. Bare nanoneedles detected dopamine in the range from 100 to 1000 mu M by differential pulse voltammetry, and enzyme-modified nanoneedles were able to respond to glutamate in the 100-500 mu M range by potentiostatic amperometry.